I was messing around with the different languages, and was in Shakespearian English, when I ran /fill. I do one coordinate point at a time, so get an error message before putting in the second point and block to fill with. I was reading it later, and I saw that what was misspelled.

This is a very simple bug to reproduce, as you just have to do "/fill ~ ~ ~" and then hit enter while your language is Shakespearian English, and look at the message that comes up. 

I have not tested this on the snapshots, but I will later today.